1. Field of the Invention
The present invention relates to device drivers, and more particularly, to device drivers for use with Accelerated Graphics Port chipsets.
2. Description of the Related Art
Personal computer systems in general and IBM compatible personal computer systems in particular have attained widespread use for providing computer power to many segments of today's modern society. A personal computer system can usually be defined as a desk top, floor standing, or portable microcomputer that includes a system unit having a system processor and associated volatile and non-volatile memory, a display device, a keyboard, one or more diskette drives and a fixed disk storage device. One of the distinguishing characteristics of these systems is the use of a system board to electrically connect these components together. These personal computer systems are information handling systems which are designed primarily to give independent computing power to a single user (or a relatively small group of users in the case of personal computers which serve as computer server systems) and are inexpensively priced for purchase by individuals or small businesses.
One aspect of the computer system that has received attention is the interface between the system unit and the display device. It is desirable that this interface be as fast and efficient as possible because this interface determines what a user sees when operating the computer system. To this end, a number of protocols and standards have been developed to increase the speed and efficiency of the interface between the system unit and the display device. One such standard is the Accelerated Graphics Port (AGP) interface standard.
The AGP interface standard provides a high performance, component level interconnect which is targeted at three-dimensional (3D) graphical display applications. The AGP interface standard is based on a set of performance extensions or enhancements to a PCI bus architecture. More specifically, the AGP interface standard provides for deeply pipelined memory read and write operations, which hides memory access latency, demultiplexing of address and data on a Peripheral Component Interconnect (PCI) bus to improve efficiency and timing for transfer rates that are faster than that of the PCI bus. These enhancements are realized through the use of sideband signals. The AGP interface is intended to provide a dedicated visual display device connection where all other input/output (I/O) devices remain on the PCI bus. The AGP interface standard is set forth and defined by the Accelerated Graphics Port Interface Specification, which is provided by Intel Corporation. The implementation of the AGP interface standard by a particular chipset includes an AGP chipset device driver which is called when access to the interface is desired.
Some operating systems are known to provide a central repository for all program setting and options within an operating system. For example, with the WINDOWS 95 and WINDOWS 98 operating systems available from Microsoft Corp., a file referred to as the Registry is provided to hold all this information. The Registry is a database that contains entries for application settings as well as WINDOWS 95 settings and preferences. Many of these values are generated by selecting customization options in, for example, the Control Panel of WINDOWS 95. Information that is stored in the Registry includes hardware settings, object properties, operating system settings and application options. For the purposes of this invention, WINDOWS 95 and WINDOWS 98 are substantially the same.
The Registry includes at least two portions, a user portion and a system portion. The user portion, which is stored in a file named user.dat, stores user specific information such as Control Panel settings, Desktop icons, Start menu folders and shortcuts, Explorer configuration, settings for Windows 95 accessories and Network connections and passwords. The system portion, which is stored in a file named system.dat, stores system specific information such as various hardware classes that Window 95 recognizes, devices attached to the computer for each hardware class, Resources (e.g., IRQs, I/O ports, and DMA channels) that are used by each device, Plug and Play information, protected-mode device drivers that are loaded at startup, internal Windows 95 settings and settings for specific 32-bit applications.